Natural energy is available throughout the world in various forms such as wind, solar, tidal and wave energy. Wind turbines have been used for production of electricity although such use has typically been limited to the production of small amounts of direct current (DC) electricity.
Conventional sources of energy for the production of electricity are in an ever-dwindling supply, which necessitates that natural forms of energy be utilized to a greater extent. The natural forms of energy are effectively inexhaustible and are typically available in different forms throughout the world.
The first machine to generate electricity from wind was designed and built in Denmark in 1890. Subsequently, several hundred machines were built in that country.
In the United States, wind machines were widely used to generate electricity in rural areas until the 1930's, providing farmers with electricity, when the US Congress enacted the Rural Electrification Act, which effectively electrified the country.
In 1931, in the (then) Soviet Union, the first relatively large wind turbine of 100-kilowatt capacity was built.
In 1941, in the United States, a 1,250-kilowatt wind machine was designed and built. Shortly after beginning the operation, a main bearing and a blade failed. Because of World War II, the machine was never repaired and it was subsequently dismantled.
Today wind turbines for producing electricity are widely used in some countries. In 2007 Germany was a leading power in wind energy production followed by USA:
1. Germany—22.248 MW, 2. USA—16.818 MW, 3. Spain—15.145 MW, 4. India—8.000 MW, 5. China—6.050 MW.
In 2008 the leading German firm Enercon began installation of the world's largest wind turbine Enercon E-126 with a power of 6-megawatt (MW) which is enough to supply electricity to 4,500.—homes. The diameter of the rotor of E-126 is 126 meters. The weight of the nacelle (gondola) is 75 tons. The tower is almost 200 meters tall. For comparison, the Eiffel tower is 300 meters tall.
Today most of the contemporary machines in the world are of the horizontal-axis wind turbine (HAWT) type; only less than 10% are of the vertical-axis (VAWT) type.
Wind turbines convert the kinetic energy of the wind into mechanical power through the use of a rotor that spins a shaft. The shaft is connected to a generator that converts the mechanical power into electricity.
The horizontal-axis type machines, in addition to the tower and the foundation include:                Blades which consist of aluminum reinforced with fiberglass. They have a heavy composite cross section which now reaches 8 cm for 2 to 3 MW production machines.        A hub which connects the blades to the low-speed shaft. The hub transmits the torque developed by the rotor blades to the shaft.        A pitch-control assembly for tilting the blades in the hub in order to properly adjust them to the so-called “angle of attack” of the wind. This means that the total surface area of the blade's assembly facing the wind changes. When the wind is weak, the surface gets bigger. When the wind is strong, each blade turns on its base and the total surface area gets smaller to reduce the wind pressure in order for the blade assembly to rotate with a constant speed.        A brake designed to stop the spinning main shaft in case of high winds. Usually a disc brake, similar to the one in automobiles.        A gearbox that converts the shaft's high-torque low-speed motion into low-torque high-speed motion that fits the electric generator's requirement. The shaft rotates on average at about 12 to 22 rpm while the generator requires approximately 1,800 rpm.        A generator, whose function is to convert the shaft torque into electricity.        A nacelle consisting of a cabin that houses all of the above mentioned elements. In modern turbines the nacelle is often of the size of a school bus or bigger. The nacelle sits atop a tower, such as a tubular steel or concrete tower or a lattice tower. Presently there is a trend is to use taller towers because the wind energy typically exponentially increases with the height.        A yaw assembly whose function is to support the entire machine assembly inside the nacelle on top of the tower and to permit its rotation for alignment with the wind.        
This clearly illustrates that converting wind energy directly into electricity utilizing wind turbines involves elaborate equipment and requires high initial costs.
Prior Technology:
As the need for storing energy increased, in 1979 Hanley patented an invention in which wind energy is used to produce electricity that is used to lift water from downstream to upstream of a dam with a hydropower plant. The lifted water is stored as potential energy. Upon demand, the water is used to generate electricity.
His invention addresses the problem of storing wind energy as water potential energy. However, it has the disadvantage of converting wind energy to hydraulic power. Therefore, Hanley's invention, assuming its technical feasibility, involves elaborate equipment and requires high initial costs.
In an effort to make offshore wind power facilities even more reliable, Siemens Energy is now testing a new type of wind turbine that works without a gearbox. The main benefit of the new unit lies in its more simplified design, which requires fewer machine components, and will therefore result in lower maintenance costs and a higher level of reliability. This is especially important for offshore facilities, where turbine breakdowns are always very expensive.
The first of the wind turbines without gearboxes has been erected in 2008 in western Denmark. This turbine has an output of 3.6 megawatts (MW). With a rotor diameter of 107 meters.
The project is in a research phase for two years and will enable Siemens Energy to determine whether or not the units without gearboxes will be able to compete with conventional models and, if so, in which performance classes. Wind turbines without gearboxes are generally heavier than conventional units and also more expensive to produce.
The units without gearboxes are instead equipped with synchronous generators that are stimulated by so-called permanent magnets. They directly convert the rotor's movements into electrical energy. The two generators in Denmark boost a torque of roughly 2,500 kilonewton-meters each. By comparison, a powerful electric drive system for a car has torque of significantly less than one kilonewton-meter.
Deficiency of Prior Technology:
The advantages of wind energy are that it is renewable, nonpolluting, and free.
The disadvantages of wind energy are that it is diluted, unpredictable, and requires high initial costs. When wind is not blowing, the wind producing equipment sits idly by and there is no electricity. Wind energy is only available when the wind is blowing within a particular range of wind speeds, i.e., the turbine cannot operate at wind speeds (also called velocities) below the minimum speed and cannot safely operate above the maximum speed. Typically, the minimum speed is 7-8 km/h and the maximum speed is 60 km/h. Hence, the wind energy is only available intermittently. Further, wind power is dependent on the location because it is only seasonal in many areas of the world.
The major disadvantages of the currently used wind turbines are:                Each has its own electric generating equipment, a gearbox linked to an AC generator atop a tower. Electric equipment is very heavy and expensive and therefore initial cost is very high. Gearboxes for contemporary wind turbines are very big, heavy and expensive machineries. There are two more problems with them. Presently the market demand for them is too high and their availability is insufficient. The manufacturing capacity lags behind the demand about 2 years. And because said gearboxes and generators are big and heavy, it is difficult to lift them to the top of today's tall wind turbine towers. Also, because of their weight and size, the construction of the towers must be very robust. Another object of this invention is to eliminate them altogether in some specific embodiments.        Each has its own pitch-control assembly. Some smaller turbines are without said assembly. They have a so-called fixed pitch wind turbine rotor. A fixed pitch wind turbine rotor is a simplification at a lower cost over that of a controllable blade pitch wind turbine rotor. However, a fixed pitch rotor is harder to start because the blade pitch for efficient operation is different from that for good starting. A proposed solution to bring the wind turbine rotor up to operating speed is to use its own generator as a motor during startup. A fixed pitch turbine rotor is designed to stall in high winds in order to limit rotor torque and not to damage the generator. This invention eliminates the pitch-control assembly.        The machines are too big, tall and bulky. For example, on a large 5 MW turbine the blades alone could be over 18 tons even with the use of carbon fiber reinforcement. The blades diameter now reaches over 120 meters. The generator alone could be over 55 tons.        The tall towers and blades up to 65 meters long are difficult to transport. Transportation can now cost 20% of equipment costs.        
In horizontal-axis wind turbines (HAWT), the electric generating equipment is installed atop the tower. The present day towers are very tall which makes installation difficult and sometime impossible in remote and high elevation locations because there are not adequate roads for big cranes to get there to deliver and install the heavy equipment. However, high elevations are the best for harvesting wind energy because of continuous high winds there. Besides the problems with installation, the operation and maintenance on the top of large towers is difficult. The blades are also subject to high vibrations during wind gusts and often bend or break apart. All of this shortens the equipment's life span.                The majority of HAWTs use an upwind design, with the rotor facing the wind in front of the tower. Downwind variants suffer from fatigue and structural failure caused by turbulence when a blade passes through the tower's wind shadow.        The electricity produced by the windmills must be consumed immediately. Usually wind blows harder at night. The demand for electricity at night is lowest. This creates an operational problem for the utility to whose grid the windmills are connected.        When wind is not blowing, the entire system is not working and no electricity is produced.        